The present invention relates to data storage systems and, more particularly, to a data storage system having a slider with features for reduced slider-media impact.
Data storage systems such as disc drives are well known in the industry. Such drives use rigid discs, which are coated with a magnetizable medium for storage of digital information in a plurality of circular, concentric data tracks. The discs are mounted on a spindle motor, which causes the discs to spin and the surfaces of the discs to pass under respective hydrodynamic (e.g. air) bearing disc head sliders. The sliders carry transducers, which write information to and read information from the disc surfaces.
An actuator mechanism moves the sliders from track-to-track across the surfaces of the discs under control of electronic circuitry. The actuator mechanism includes a track accessing arm and a suspension for each disc head slider. The suspension includes a load beam and a gimbal. The load beam provides a load force which forces the slider toward the disc surface. The gimbal is positioned between the slider and the load beam, or is integrated in the load beam, to provide a resilient connection that allows the slider to pitch and roll while following the topography of the disc.
The slider includes a hydrodynamic (e.g. air) bearing surface, which faces the disc surface. As the disc rotates, the disc drags air under the slider and along the bearing surface in a direction approximately parallel to the tangential velocity of the disc. As the air passes beneath the bearing surface, air compression along the air flow path causes the air pressure between the disc and the bearing surface to increase, which creates a hydrodynamic lifting force that counteracts the load force and causes the slider to fly above or in close proximity to the disc surface.
In ramp load-unload applications, the disc drive further includes a ramp positioned at an outer diameter of the disc for engaging the suspension. When the disc drive is powered down, the actuator mechanism moves the suspension radially outward until the suspension engages the ramp, causing the slider to lift off of the disc surface. In the case of a slider having a subambient pressure cavity, the suspension and slider must overcome the suction force developed by the subambient pressure cavity (which tends to pull the slider toward the disc) in order to lift the slider up the ramp. During power-up, the disc is accelerated to its normal operating velocity and then the actuator mechanism moves the suspension radially inward such that the suspension disengages the ramp allowing the slider to become loaded on to the disc surface.
Using a ramp to load and unload the suspension relative to the disc surface has been regarded as an attractive alternative to “contact start/stop” technology in which the slider lands and takes-off from a dedicated zone on the disc surface. The ramp load-unload technique can be used for solving tribological problems associated with lower fly heights and for meeting severe requirements of non-operational shock performance. However, this technique introduces an array of other challenges, such as possible severe head-media impact during loading and unloading operations.
Under nominal conditions, advanced air bearings (AABs) can be designed to avoid head-media contact during load and unload. Manufacturing of actual parts, however, introduces deviation from nominal conditions, which can result in larger susceptibility of impact during load-unload operations. Among the numerous dimensions and geometrical features to be controlled during manufacturing, pitch static attitude (PSA) and roll static attitude (RSA) are the most critical parameters for load-unload applications. PSA is the angle formed between the slider and the suspension in a direction parallel to the suspension's axis of symmetry when no air bearing is formed (i.e., in a “static” state). RSA is the angle formed between the slider and the suspension in a direction perpendicular to the suspension's axis of symmetry.
Since PSA and RSA have an influence on the pitch and roll attitude of the slider during flight, manufacturing tolerances that result in a non-optimal PSA or RSA cause the slider to tilt with respect to the radial motion of the suspension during loading and unloading operations. Under these conditions, it is possible that the corners of the slider can become close enough to the media to induce light contact or severe impact. When the slider is being loaded onto the disc, a corner or edge of the slider can contact the disc before an air bearing has been developed. During unloading, imbalances between the suction force and the lift force can also cause the slider to contact the disc. This contact can cause damage to stored data, thermal asperities and permanent physical damage to the slider and disc surfaces.
Similarly, in a contact-start-stop system, a corner of the slider can contact the disc in response to shock forces applied to the disc drive or other events that cause a variation in the flying height of the slider. Any such contact leads to wear of the slider and the recording surface and is potentially catastrophic.
One method of reducing damage caused by contact between the slider and the disc is to provide landing pads on the slider, which have a smoother contact surface than the etched surfaces on the slider body. The landing pads can be below or within the pressurization plane of the bearing surface. Another method of reducing damage caused by contact between the slider and the disc is to provide the bearing surface with at least one rounded corner. Also, the non-bearing surfaces can be provided with at least one rounded edge or a deeply recessed corner. As a result, the disc surface is less likely to be damaged when hit by the rounded corner or edge than a sharp corner or edge.
However, strong contact can still occur with the above-mentioned methods due to inadequate pressurization at different PSA and RSA conditions. A slider is therefore desired that avoids or reduces contact with the disc surface during operational shock events and/or during load and unload operations.